1. Technical Field
The present invention relates in general to abating noise during the release of high pressure fluids and, in particular, to an improved system, method and apparatus for fluidic effectors that provide enhanced exhaust plume mixing for jet engines.
2. Description of the Related Art
A nozzle exhaust has high temperature and high velocity. The high temperature of the exhaust plume reduces the durability of the nozzle material, and the high velocity produces a significant amount of jet noise. As shown in FIG. 5, a conventional nozzle 51 produces an exhaust plume 53 having a core 55. Small-scale eddies 57 produce high frequency noise downstream from nozzle 51, and large-scale eddies 59 produce low frequency noise further downstream from nozzle 51.
A common way to reduce the exhaust plume temperature and the jet noise is to use an ejector nozzle. Ejector nozzles mix ambient air with the nozzle exhaust. This type of nozzle is typically heavy, bulky and complex, and inherently reduces performance of the engine.
For example, FIG. 1 depicts an aircraft nozzle 11 that incorporates an internal ejector mixer. A lobed mixer 13 (FIG. 2) also may included. A scoop 15 is formed in the nozzle 1 to duct ambient air flow 17 into the exhaust stream 19. The exhaust stream and the ambient air channeled through multiple lobes 21 in the mixer 13 that alternate hot and cold jets to mix the fluids within a constrained duct 23. However, ejector nozzle 11 may be located internally or externally with respect to a jet engine. To incorporate this design inside a jet engine, the internal nozzle geometry is typically modified to a larger diameter than the basic engine. As a result, this solution requires a heavier and more expensive configuration to handle the thermal environment. This design also has an associated thrust-loss penalty at the nozzle (i.e., internal) and a drag penalty (i.e., externally) because of the increase in size requirements.
FIG. 3 illustrates an ejector nozzle solution having delta-shaped tabs 31 (e.g., one shown) protruding into the core exhaust stream at the nozzle exit 33. This design produces many small vortex pairs and has an associated thrust-loss penalty as the exit flow is impeded. Moreover, this solution has limited applicability due to the extreme thermal environment inflicted on the tabs 21.
FIG. 4 depicts one or more saw-toothed trailing edges 41, 43 (e.g., two shown) on an aircraft engine 45. Depending on the application and by-pass ratio (BPR), this design imparts weight penalties and constant drag. In addition, this solution generates the least beneficial stream-wise vorticity of these conventional designs. Thus, an improved design for fluidic ejector nozzles that provides enhanced plume mixing would be desirable.